1. Field of the Invention
In one aspect, the invention relates to a coaxial needle assembly for the placement of a cannula within a tissue prior to a biopsy procedure.
2. Description of the Related Art
A biopsy is a well-known medical procedure that involves taking a sample of tissue from a person and examining it for diagnostic purposes. The biopsy is often done when an abnormality, such as a lesion, is found in a tissue mass, using an imaging system, such as mammography or ultrasonography, or other methods of detection. While biopsies can be used for many different purposes, examining a sample of tissue from an abnormal site is one way to accurately diagnose whether the site is cancerous. In the case of suspected cancer, particularly cancer of the breast, early detection and diagnosis is critical to the success of the patient's treatment and recovery.
One biopsy technique frequently performed is a core biopsy, which uses a biopsy device in which a tissue specimen is captured in a coring cannula that is advanced into the tissue mass to the site of the abnormality. Some biopsy devices use a notched biopsy stylet that is inserted into a lesion, such that tissue prolapses into the notch on the biopsy stylet, with the coring cannula then advancing over the notch to cut a tissue sample. Other devices use just a coring cannula, which requires moving the end of the coring cannula to effect severing of the tissue sample from the surrounding tissue mass. Another device advances a spoon into the tissue mass, which is then followed by a coring cannula having a cutting finger, which is rotated to sever the tissue sample. Such a device can be found in commonly assigned U.S. Patent Application Publication No. 2006/0030785, entitled “Core Biopsy Device”, which is incorporated herein by reference in its entirety. The biopsy cannula and stylet, if used, with the tissue sample, is then removed from the tissue, and the tissue sample is examined.
It is often necessary to take multiple tissue samples from the lesion and/or the surrounding area. To avoid having to puncture the skin for every tissue sample, a coaxial needle assembly is placed in the tissue prior to use of the biopsy device to act as a guide for the biopsy device. A coaxial needle assembly commonly includes a needle cannula defining a lumen in which a stylet is received to close off the open distal end of the needle cannula during insertion to prevent unwanted coring of the tissue. After insertion, the stylet is removed and the biopsy cannula and stylet/spoon of the biopsy device are inserted through the needle cannula and into the lesion to take a tissue sample. The biopsy device is then removed from the tissue, and the needle cannula can be manipulated to a new location within the tissue mass so that upon reinsertion of the biopsy device, a tissue sample can be taken from a different area of or surrounding the lesion.
The coaxial needle assembly is commonly placed using an imaging device. The placement normally locates the tip of the needle cannula at the desired location relative to the lesion. The biopsy device and needle cannula can be configured such that the biopsy device is aligned relative to the needle cannula to insure that upon actuation of the biopsy device, the biopsy specimen will be taken at a known distance from the tip of the needle cannula. A common way of accomplishing the alignment is to insert the biopsy device into the needle cannula until the biopsy device aligns with a reference point on the needle cannula. This can be done by aligning marks on the biopsy device and needle cannula or by inserting the biopsy device until it abuts the needle cannula. In most cases, the tip of the biopsy device's cannula/stylet is aligned with the tip of the needle cannula when the biopsy device and needle cannula are aligned. The reference points are external of the tissue mass, whereas the tips of the biopsy device and needle cannula are internal of the tissue mass, which provides the user with an externally visual method of aligning the internal tips, which are not visible other than using an imagining device.
The position of the needle cannula determines what tissue will be sampled by the biopsy device, since the biopsy cannula will protrude from the end of the needle cannula to take a tissue sample. Therefore, for current systems the alignment is dependent on the length of the needle cannula being the same as or a fixed length relative to the biopsy cannula prior to taking a tissue sample.
The current alignment approach is not compatible with biopsy devices having adjustable length biopsy specimens, especially those that increase the relative length of the cannula or stylet to adjust the length of the specimen. If the length of the biopsy device's cannula or stylet is extended/retracted relative to the supporting body to effect the specimen length adjustment and the abutment of the supporting body with the needle cannula is used for alignment, the biopsy device's cannula or stylet will be over/under inserted relative to the cannula needle. As such, it becomes necessary to account for the difference in lengths between the biopsy cannula and stylet and the needle cannula, which has a fixed length. This is difficult, since the user cannot view the position of the cannulas within the body and must rely upon external cues to verify that the biopsy cannula is correctly positioned within the needle cannula.
Another issue is that manufacturers of biopsy devices and coaxial needle assemblies often have unique ways of measuring the length of their respective cannulas. It is therefore difficult to use one manufacturer's biopsy device with another manufacturer's coaxial needle assembly.